Bone marrow transplant (BMT) is an extraordinarily rapid growing field and the number of transplants in the US is expected to grow from a current rate of 15,000 per year to over 100,000 per year by 1995. This rapid expansion is due to the diversity in the types of bone marrow transplantation procedures and the number of clinical procedures that can be benefitted by a BMT. A major limiting factor in BMT therapy is the high cell number that is needed for reingraftment, and traumatic procedure needed for cell aspiration and the poor capability to handle cells ex vivo. Cells are basically frozen during ex vivo storage. Thus, significant need exists for the development of ex vivo hematopoietic cell expansion technologies. The investigators have developed cell culture conditions under which human hematopoietic cells expand ex vivo. Based on this discovery, we wish to develop clinically useful systems to improve BMT procedures. The first step in the development of a clinical- scale system is to make small hematopoietic bioreactor systems that mimic and successfully reproduce the expansive cell culture conditions. We propose to develop and optimize such a prototype hematopoietic bioreactor system with Phase I funding. If the goals of Phase I are successfully met, we will pursue a Phase II study to develop clinically useful prototypes.